Research Papers

Process Parameter Effects on Dimensional Accuracy of Micro-Injection Moulded Part

[+] Author and Article Information
M. R. Mani, J. Segal, S. Ratchev

Manufacturing Research Division,
Faculty of Engineering,
University of Nottingham,
Nottingham NG7 2RD, UK

R. Surace

Institute of Industrial Technology and Automation,
National Research Council, Bari 70124, Italy

I. Fassi

Institute of Industrial Technology and Automation,
National Research Council,
Bari 70124, Italy

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF Micro- AND Nano-Manufacturing. Manuscript received September 12, 2012; final manuscript received July 18, 2013; published online August 12, 2013. Assoc. Editor: Liwei Lin.

J. Micro Nano-Manuf 1(3), 031003 (Aug 12, 2013) (8 pages) Paper No: JMNM-12-1056; doi: 10.1115/1.4025073 History: Received September 12, 2012; Received September 12, 2012; Revised July 18, 2013

Micro-injection moulding is becoming increasingly important among the available processes for production of micro-electromechanical systems (MEMS) and microsystem technologies (MSTs), and higher number of polymer products is being manufactured by this process. Due to the sensitive nature of applications of this process, such as medical and aerospace applications, achieving high quality parts with high dimensional accuracy is crucial. In this work, a design of experiment (DoE) approach is used. The aim is to study the effects of three process parameters which are commonly used for research in this domain, on the dimensional accuracy of microchannels with different sizes; they are injection velocity, injection pressure, and melt temperature. The study focuses on two polymers, polyoxymethylene (POM) and liquid crystal polymer (LCP). Experimental results showed that higher melt temperature and injection pressure resulted in higher dimensional accuracy. Nevertheless, high settings for the three parameters resulted in higher percentage of flash in most cases. In conclusion, the most influential factors were shown to be melt temperature and injection pressure.

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Fig. 1

Picture of the mould (a) assembled mould (b) pin inserts

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Fig. 2

Schematics of the channels on the pin

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Fig. 3

Measurement points for small (S) and large (L) dimensions of the channels and flash (F)

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Fig. 4

Samples of pin 1 manufactured in POM

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Fig. 5

SEM images of pin 1A manufactured in (a) LCP (T = 330, V = 300, P = 600) and (b) POM (T = 230, V = 250, P = 700)

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Fig. 10

Main effect plot (a) and interaction plot (b) for dimensional error

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Fig. 11

Pareto chart for dimensional error

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Fig. 12

Main effect plot (a) and interaction plot (b) for flash

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Fig. 6

Dimensional error for pins 1 and 2 LCP

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Fig. 7

Dimensional error for pins 1 and 2 POM

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Fig. 8

Percentage flash for pins 1 and 2 LCP

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Fig. 9

Percentage flash for pins 1 and 2 POM

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Fig. 13

Pareto chart for flash

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Fig. 14

Melt viscosity comparison Vectra LCP versus semicrystalline polymers



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